TITLE: Temporomandibular Joint Disorders
SOURCE: The University of Texas Medical Branch
DATE: March 11, 1998
RESIDENT PHYSICIAN: Michael E. Prater, MD
FACULTY PHYSICIAN: Byron J. Bailey, MD
SERIES EDITOR: Francis B. Quinn, Jr., MD

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"This material was prepared by physicians in partial fulfillment of educational requirements established for Continuing Postgraduate Medical Education activities and was not intended for clinical use in its present form. It was prepared for the purpose of stimulating group discussion in a interactive computer mediated conference setting. No warranties, either express or implied, are made with respect to its accuracy, completeness, or timeliness. The material does not necessarily reflect the current or past opinions of subscribers or other professionals and should not be used for purposes of diagnosis or treatment without consulting appropriate literature sources and informed professional opinion."


Although no specific data exists regarding the social impact of temporamandibular joint disorders, TMJ is estimated to account for as much as thirty billion dollars a year in lost productivity. Americans lose 550 million work days every year due to symptoms associated with TMJ, with facial pain and headache being the most common complaints. Accordingly, analgesics directed at these symptoms are among the top selling over the counter medicines in our society.

Despite the lack specific data regarding the incidence of these disorders, much has been learned over the last decade regarding specific pathology and therapy. Generic terms such as TMJ Syndrome, or Myofascial Pain Dysfunction Syndrome (MPD Syndrome) are generally outdated. It is now possible to differentiate between true muscular disorders and those disorders with pathological changes of the temporomandibular joint.

The term temporomandibular joint disorders is an umbrella term which combines those with true pathology of the temporomandibular joint and those with involvement of the muscles of mastication (myofascial pain dysfunction). Much of the difficulty encountered with the treatment of these patients is attributed to the physicians inability to accurately diagnose the disorder.

Anatomy

Painful disorders of the temporomandibular joint involve the trigeminal nerve. There are three branches of the nerve that have their sensory synapses in the trigeminal ganglion: the ophthalmic (V1), maxillary (V2) and mandibular (V3). Each branch also contains motor fibers, which innervate the muscles of mastication. Pain receptors are divided into two groups, depending on their size, myelination and rate of transmission. The larger A delta fibers are myelinated and therefore transmit pain quickly, and are the most important pain fibers. The smaller, nonmyelinated fibers, or C fibers, are more susceptible to chronic, dull, pain and pressure. Both pain fibers have input from the trigeminal ganglia to the spinal nucleus, with subsequent synapses leading to the postcentral gyrus and the reticular activating system. This helps explain the highly emotional component of facial pain.

Other areas innervated by the trigeminal nerve helps explain referred pain from the temporomandibular joint. Included are the dura mater, orbit, paranasal sinuses, tympanic membrane, oral cavity and teeth, helping explain headaches, eye pain, sinus pressure, otalgia and dental pain, respectively.

The muscles of mastication are abductors (jaw opening) and adductors (jaw closing) muscles. The temporalis, masseter and medial pterygoids are adductors, while the lateral pterygoids are the primary abductors of the jaw.

The temporomandibular joint consists of the mobile condyloid process of the mandible which articulates with the glenoid fossa of the temporal bone. The anterior portion of the glenoid fossa is the articular eminence. Posteriorly lies the external auditory canal. Laterally is the zygomatic process, and medially is the styloid process. The surface of the condylar and glenoid fossae are lined with fibrous connective tissue which is primarily a layer of hyaline cartilage. This thin, unprotected cartilage, particularly on the condylar process, is an important growth center. Damage to this cartilage can result in dysmorphic growth of the mandible and, by extension, the maxilla. Therefore, any alteration in the cartilaginous layers in a child is a cause for great concern regarding facial growth.

Between the condylar process and the glenoid fossa lies an interposed cartilaginous disc. The disc provides a stable platform for the rotational and gliding movements of the joint. It also acts as a shock absorber. An alteration in the normal position of the disc is known as an internal derangement. The mandible is held in position by a set of several ligaments. Medially and laterally are the capsular ligaments, and posteriorly is the meniscotemporomandibular frenum (retrodiscal pad). More posteriorly and medially are the stylo- and sphenomandibular ligaments. Finally, the tendons of the muscles of mastication also suspend the mandible.

In the healthy joint, the disc and condyle are considered one continuous anatomical structure. The lateral and medial ligaments and the retrodiscal pad have connections between the disc and the condyle. Therefore, the essential cause of disc disorders is a pathologic change in the ligamentous attachments of the disc-condyle complex..

Anterior to the condyloid process is the coronoid process of the mandible. The notch between the two is known as the incisura mandibularis, or the sigmoid notch. The temporalis tendon inserts along the coronoid process, and the masseter has a broad insertion along the lateral border. Passing over the sigmoid notch is the masseteric artery, a branch of the maxillary artery, which along with other branches of the internal maxillary artery supply the joint capsule.

Diseases and Disorders of the TMJ

The temporomandibular joint is susceptible to all the conditions that affect other joints in the body, including ankylosis, arthritis, trauma, dislocations, developmental anomalies and neoplasms. Although treatment is often similar to other joints in the body, some variations exist.

Myofascial pain disorders are the most common cause of pain in the head and neck, and those involved in the temporomandibular joint are no exception. The complex symptomatology and frequent psychosocial factors often make these disorders difficult to treat. Once diagnosed, however, treatment is usually effective if compliance is maintained. The muscles of mastication are primarily involved, and the condition is characterized by a unilateral dull, aching pain which increases with muscular use. Common complaints associated with referred pain include headache, otalgia, tinnitus, burning tongue and sometimes decreased hearing.

There is believed to be a large psychosocial component of this disease. Increased stress levels are believed to result in poor habits, including bruxism, clenching and even excessive gum chewing. These lead to muscular overuse, fatigue and spasm, and subsequently, pain.

Muscular disorders consist of a group of diagnoses that are characterized by pain from pathologic or dysfunctional changes in a muscle group, and there are at least six recognized disorders of the head and neck. Myositis is an acute condition with inflammation of the muscle and connective tissue with associated pain and edema and a decreased range of motion. Etiologies include overuse, infection or trauma. Muscle spasm is considered an acute contraction of a muscle caused by an overstretching or overuse of a muscle. If left untreated in the contracted state, fibrous scarring and contracture will develop. Hysterical trismus refers to decreased range of motion which is due to psychological causes. Fibromyalgia is a diffuse, systemic muscular process whereby areas of firm, painful bands are found in weight bearing muscles, often with an associated sleep disorder. There is no evidence of arthritis or myositis, and there is a female preponderance. There is often associated bruxism and arthritis, and the most common areas affected are the back, head and neck, abdomen and extremeties.

Myofascial pain syndrome (MPS) may be considered a localized form of fibromyalgia in the head and neck. There are three diagnostic criteria:

  1. the presence of painful, firm bands of muscle or tendons, termed trigger points;
  2. pain complaints that follow known patterns of referral of trigger points, and
  3. reproducible pain complaints with trigger points.
Collagen diseases such as systemic lupus erythematosis, Sjogrens syndrome, scleroderma and arthritis also cause muscular pain in the head and neck. Lupus is characterized by a butterfly rash of the face, fever, rheumatoid arthitis and pleural and abdominal pain. Laboratory studies reveal a high sedimentation rate, hypochromic anemia, a positive ANA test and a false-positive VDRL. Scleroderma is characterized by gradual onset of muscle and joint pain leading to a systemic sclerosis with anorexia, dyspnea and diminished sweating. Fever, skin lesions and limited jaw and chest expansion are seen.

Sjogren's syndrome is characterized by dryness of the mouth, eye and skin and oftentimes, muscle and joint pain. Rheumatoid arthritis is a chronic inflammation of the synovial membrane with pain in the muscles and joints. Numerous joints in the body are usually affected, and pain usually decreases with use. Fatigue, fever, muscle pain, night sweats and sometimes weight loss are seen. Studies show the presence of rheumatoid factor, and increased sedimentation rate and antinuclear antibodies.

The treatment of myofascial pain is divided into four phases. Phase one treatment is initiated upon diagnosis, and consists of educating the patient on muscle fatigue and spasm as the cause of pain and dysfunction. It helps to explain referred pain. The avoidance of clenching and grinding is emphasized, and a soft diet is instituted. Nonsteroidal antiinflammatory agents are prescribed, with or without a muscle relaxant. The most commonly used agents are valium and ibuprofen. One half of patients will obtain significant relief in 2-4 weeks. Phase II therapy is initiated if phase I treatment fails. Medications are continued, but a bite appliance (splint) is added. This helps prevent muscle overuse, including bruxism. The appliance is usually worn at night, but can also be worn during the day if necessary. Care should be taken to instruct the patient not to wear the appliance at all times, as the posterior teeth may become displaced. An additional 25% of patients will receive relief with this therapy. Once relief is obtained, the medications are discontinued.

If the patient remains asymptomatic, the appliance is discontinued. If symptoms return, the appliance may be resumed at night, and its use continued as long as necessary. If phase II therapy alone fails, physical therapy of the muscle groups, including ultrasonic therapy, electrogalvanic stimulation or biofeedback are added. No one form of treatment is superior. Another 15% of patients will find relief within four weeks. If phase III therapy fails, psychological counseling is advised to identify stresses, and patients are referred to a TMJ center. TMJ centers employ a multidisciplinary approach, including psychological counseling and trigger point injections, for treatment.

Joint disorders are the second most common cause of persistent head and neck pain. Included are internal derangements, degenerative joint disease and inflammation of the joint space (capsulitis). The greatest difficulty facing the clinician is distinguishing these disorders from those involving the muscles, since the presentations are often similar. Those with TMJ arthropathy often present with the additional finding of clicking or popping on opening or closing of the jaw. Oftentimes, a history of lock jaw can be elicited. Sometimes, the chief complaint is not a pop, but an occlusal instability associated with locking. These signs are highly suggestive of a joint disorder.

The most common TMJ arthropathy is the internal derangement, which is characterized by a progressive anterior disc displacement. It is often associated with a capsulitis, making pain a common feature. On physical exam, a popping is felt and heard, with associated pain.

The most common derangement is anteromedial, and the degree of derangement generally correlates with symptoms. Donlon divided derangements based on findings of history and physical exam. Myofascial pain is associated with pain over the temporomandibular joint without a palpable or audible click. A type IA derangement is found with a popping over the joint without associated pain. It is seen in over 50% of normal subjects. A type IB derangement is popping of the joint associated with pain. The popping is due to the noise the condyle makes as it moves under the anteriorly displaced disc. The pain is due to the stretching and subsequent inflammation of the retrodisc pad.

The type II derangement is similar to a type IB derangement, but a history of lock jaw can be elicited. There are two types of lock jaw. The closed lock is due to the inability of the condyle to slide under the anteriorly displaced disc. The open lock is due to the inability of the condyle to slide back over the disc into its normal position. A type III derangement is a persistent lock, usually closed. Hence, there is usually no associated click or pop on physical exam. Of note, these symptoms are usually progressive. The patient often gives a history of having passed through each type of derangement.

Early treatment of the internal derangement is imperative, as progression of disease leads to a less favorable prognosis. Therapy for type I and II derangements is similar to that for myofascial disorders. NSAIDs and muscle relaxers (valium) are prescribed as is the instruction of a soft diet and jaw rest. Failure of these methods requires the addition of a splint to attempt the repositioning of the condyle. The purpose is to reposition the condyle into a more favorable position related to the disc. Clicking is usually not eliminated, but it may be reduced to a soft pop with reduced pain. If repositioning with a splint fails, arthoscopic or open surgical repair is recommended. The purpose of these procedures is to surgically remove adhesions and to reposition the disc into a favorable position. A type III derangement requires aggressive therapy. The joint is unlocked, usually under anesthesia. Physical therapy and an anterior bite plate is used. If no improvement results after 3 weeks of therapy, TMJ surgery is undertaken to reposition or repair the disc.

Congenital and developmental anomalies of the temporomandibular joint, although relatively rare, are important to identify early to reestablish normal midface growth centers. The more common entities include condylar agenesis, condylar hypoplasia, condylar hyperplasia and hemifacial microsomia.

Condylar agenesis is the absence of all or portions of the coronoid process, condylar process, ramus and mandibular body. Other first and second arch abnormalities are commonly seen. Early treatment is indicated to limit the degree of deformity, with the primary objective being to re-establish the condylar growth center. This is best done with a costochondral graft with or without orthodontic surgery and facial plastic augmentation.

Condylar hypoplasia may be congenital, but is usually the result of trauma or infection. The most common facial deformity is shortness of the mandible with deviation of the chin towards the affected side. Treatment of the child involves the placement of a costochondral graft. In the adult, treatment involves either shortening of the normal side or lengthening of the involved side. Both result in an acceptable cosmetic and functional result. Orthodontic therapy is necessary in all cases to establish proper occlusion.

Condylar hyperplasia is an idiopathic disease characterized by a progressive, unilateral overgrowth of the mandible. The chin is deviated towards the unaffected side. Presentation is common in the second decade. Radiographic findings are usually a normal condyle but an elongated neck. Treatment depends on whether the condyle is still growing. It growth is occurring, condylectomy is the treatment. If growth has ceased, orthognathic surgery is performed.

Traumatic injuries to the condyle are common. The diagnosis of a condylar fracture is usually made easily by physical examination and radiographic studies. A unilateral condylar or subcondylar fracture results in deviation of the jaw towards the site of fracture with opening. Minimally displaced fractures are usually treated with intermaxillary fixation with early mobilization. Displaced fractures or those that interfere with function may have to be treated with open reduction with internal fixation and intermaxillary fixation. Bilateral fractures frequently present with an anterior open bite and are usually treated with IMF and ORIF. In children IMF is the treatment of choice for severely displaced fractures, along with early mobilization. Repositioning of the condylar head may be necessary to reestablish normal midface growth.

Dislocation of the jaw is either acute or chronic. An acute dislocation results when the mandible is fixed in an open position with only the posterior teeth in contact. Treatment is reduction, usually supplemented by IV sedation, although general anesthesia may be required. Chronic recurrent dislocation is usually due to abnormally lax ligaments. Treatment is usually undertaken by injecting sclerosing agents into the joint capsule to produce a scarring and contracture of the ligaments. A capsulorrhaphy may be performed, whereby the ligaments are shortened surgically. If the cause of the chronic dislocation is an abnormally tense or shortened lateral pterygoid muscle, a myotomy is performed.

Ankylosis of the TMJ is an obliteration of the joint space with abnormal bony morphology. It is important to distinguish true ankylosis from false ankylosis, which is an extracapsular condition resulting in an enlarged coronoid process, zygomatic arch fracture or scarring from surgery. In general, severe ankylosis is treated with a prosthetic condyle. Three principles are imperative. First, the new joint should be established at the highest possible point on the ramus to maintain maximal mandibular height. Second, an interpositional material is placed to avoid fusion. Third, aggressive, long term physical therapy is important. In the child, a costochondral graft is preferred over a prosthetic joint to attempt to replace the condylar growth center.

Arthritic changes are the most frequent pathologic conditions affecting the temporomandibular joint, but most are asymptomatic. All types occur, but degenerative and rheumatoid arthritis are the most common.

Rheumatoid arthritis is usually seen in other joints prior to TMJ involvement. With progression, bilateral TMJ tenderness and swelling are seen. In early stages, there are few radiographic changes, but as the disease advances the joint space becomes progressively narrower. In end stage rheumatoid arthritis of the TMJ this joint space obliteration results in an anterior open bite. In juvenile rheumatoid arthritis with TMJ involvement, end stage disease can result in destruction of the condylar growth plate.

Treatment of rheumatoid arthritis of the TMJ is similar to other joints. Nonsteroidal antiflammatory medications are used during the acute phase along with jaw exercises once the pain subsides. In severe, chronic cases, drugs such as penicillamine and gold are used. Surgery is limited to severe, refractory ankylosis, as discussed above.

Degenerative arthritis can be either primary or secondary. Primary disease is seen in old people and is a disease of wear and tear. Patients are usually asymptomatic, and when symptomatic, the complaints are usually mild. Secondary dejenerative arthritis occurs secondary to trauma or chronic bruxism. It occurs in younger people and the symptoms are much more severe. Radiographic findings consist of a primarily unilateral lipping of the joint with osteophyte formation and erosion of the articular surface of the condyle. Again, in children, damage to the growth plate must be suspected.

Treatment of degenerative arthritis is similar to that of myofascial disorders and early internal derangements. NSAIDs and muscle relaxers with a soft diet are the primary treatment. Bite appliances are added as necessary. When conservative medical management fails to improve symptoms after a 3-6 month trial, surgery is considered. Surgical intervation includes removal of any surgical capsular abnormality, including osteophytes, until the joint space is smooth. A condylar shave is when the entire cortical plate is removed. It should be avoided if possible, as resorption of the condyle is a known complication.

Neoplasms of the TMJ are uncommon. The most common tumors are benign, and include chondromas, osteomas and osteochondromas. Rarely, fibrous dysplasia, giant cell reparative granuloma and chondroblastoma are seen. Very infrequently malignant tumors such as fibrosarcoma and chondrosarcoma are seen.

Surgery is the treatment of choice for neoplasms of the TMJ. Radiation therapy is generally ineffective.

Surgery of the Temporomandibular Joint

Surgery of the temporomandibular joint is an effective treatment for structural disorders, but the high frequency of psychosocial contributing factors and the availability of medical therapy necessitates careful patient selection. Numerous studies and guidelines exist, many of which are contradictory. At the University of Minnesota, less than 10% of patients enrolled in the chronic Craniofacial Pain Clinic have required surgery, and in general, less than 1% of all patients with symptomatic TMJ disorders require surgical intervention.

There are several general surgical indications. Documented refractory internal derangements are the most common indication. Pain and dysfunction of such magnitude as to constitute a disability to the patient is an indication, but thorough documentation and informed written and verbal consent are an absolute necessity. Prior unsuccessful medical management is also an indication. It is imperative to understand despite careful selection, psychosocial factors are believed to play a large factor in some patients.

There are five general surgical procedures:

  1. disc repair,
  2. menisectomy,
  3. menisectomy with implant,
  4. bone reduction procedures, and
  5. arthroscopy.
Disc repair procedures are recommended for minimal morphologic changes. The disc's posterior attachment is incised and the anteriorly displaced disc is repositioned posteriorly over the condyle in a more normal anatomic position. If a large articular eminence exists, smoother function may be obtained by excising a portion of the eminance or the condyle. Approximately 90% of patients achieve reduced symptoms.

Menisectomy is the removal of the disc. It is recommended when severe changes in disc morphology occur. A temporary implant may be designed to maintain disc space. About 85% of patients receive relief, but 15% require further surgery for refractory pain. A long term risk is osseous changes of the joint space.

Menisectomy with implantation involve removal of the disc with placement of a permanent interpositional implant. The implant stabilizes the joint space allowing smoother function and less risk of osseous changes. Silastic implants are most common, although proplast, temporalis fascia and auricular cartilage are also used. Some choose to remove the implant after several weeks, as scar tissue forms around the implant and acts in much the same manner as a disc. Several animal models have shown failure of these implants are associated with a significant foreign body reaction involving giant cells and other inflammatory infiltrates.

Bone reduction procedures preserve the disc through a high conylotomy or condylectomy. These procedures are designed to increase joint disc space. A condylotomy involves performing an osteomy on the neck with repositioning of the condyle. A condylectomy involves an extended condylotomy with removal of bone.

Arthroscopy is the endoscopic examination of the joint space. It is used for both diagnosis and treatment. Adhesions and loose bodies are the most common indications and findings for arthroscopic treatment of the temporomandibular joint. Advancements in techniques have allowed arthroscopy to be employed in several internal derangement procedures, including some disc procedures.

Most studies report minimal morbidity associated with TMJ arthroscopy. The most common complications include bleeding, infection and damage to the facial nerve.

Complications of temporomandibular surgery are difficult to predict. Psychosocial factors play a large role, and depression is seen. Failure to improve symptoms is the most common complaint. Infection, capsulitis, facial nerve injury, degenerative joint disease and anterior open bite are findings seen on physical exam.

Radiology

Plain films, computed tomography, magnetic resonance imaging and arthrography are the studies utilized in the TMJ. MRI is noninvasive and is the best technique for evaluating disc morphology and position. CT is useful for evaluation of bony deformaties. Plain films with or without arthrography are occasionally used. In general, fibromyalgia requires no imaging study. Type I and II internal derangements require MRI, whereas ankylosis and other bony disorders are best examined by computed tomography. Of note arthroscopy is often employed as well.

Editor's Comments:

Physical findings which support an initial diagnosis of temporomandibular arthralgia include:
  1. complete absence of molar teeth in any one quadrant,
  2. deviation of the jaw to the painful side on wide opening,
  3. reproducibility of the pain by pressure below the ear forward in the direction of the mandibular condyle,
  4. reproducibility of the pain by pressure from within the membraneous ear canal forward in the direction of the mandibular condyle, typically by reversing a laryngeal mirror and pressing with the round end of the handle in the ear canal, and
  5. reproducibility of the patient's complaint of "ear pain" by inserting two tongueblades between the opposite molars and instructing the patient to bite down hard on the tongue blades
Once the patient has come to realize that the pain is arising from the joint and not the ear, it is easier to persuade him/her to consult his dentist for occlusal equillibration, or perhaps even an occlusal splint.

BIBLIOGRAPHY

Fricton, James R., TMJ and Craniofacial Pain: Diagnosis and Management, Ishiyaku EuroAmerica, Inc., 1988.

Fricton, James R., Myofascial Pain Syndrome, Oral Surgery, 60(6): 615-623, 1992.

Bailey, BJ, Head and Neck Surgery-Otolaryngology, JB Lippincott Co, 1993.

Keith, DA Surgery of the TMJ, Oxford, 1988.

Cummings, C, Otolaryngology-Head and Neck Surgery, C.V. Mosby Co, 1993.

Paparella, et. al., Otolaryngology, W.B. Saunders Co, 1991